The website is a laggy piece of junk.
The UA website is way too "live" for its own good. I can see how it is trying to load up so many things in the background — checking to see if you're logged into MileagePlus, giving you "dynamic" results when you search for something. Once all those background processes have occurred the site runs relatively normally; the issue is that those background processes sometimes take ages, and they happen on literally *every single page* of the site! I wish it were a dumber site!
God, do I ever miss the days of old-school HTML. Navigating this thing is like navigating some bloated WordPress site that uses a million custom plug-ins that haven't been updated in years.